Non-covalent polymerisation in the solid state: halogen-halogen vs. methyl-methyl interactions in the complexes of 2,4-di(2-pyridyl)-1,3,5-triazine ligands

Fe(II), Co(II), Ni(II) and Cu(II) complexes based on the triazine ligand 2,4-di(2'-pyridyl)-6-(p-bromo-phenyl)-1,3,5-triazine have been synthesised and characterised. The electrochemical, magnetic and spectroscopic properties of the complexes have also been investigated, and the electron deficient triazine ligand has been shown to affect each of these properties. Further investigation of solid state structures of the ligand and its Fe(II), Co(II) and Cu(II) complexes has established that stabilising Br-Br interactions exist which link neighbouring molecules to form one-dimensional tapes. A slight modification of the ligand, i.e., using 2,4-di(2'-pyridyl)-6-(p-methylphenyl)-1,3,5-triazine, in which the phenyl substituent has changed from a bromine to a methyl group, eliminates the one-dimensional tape and gives rise to significant pi-stacking interactions in the solid state.     

Synthesis, structural, thermal studies and biological activity of a tridentate Schiff base ligand and their transition metal complexes

Schiff base (L) ligand is prepared via condensation of pyridine-2,6-dicarboxaldehyde with -2-aminopyridine. The ligand and its metal complexes are characterized based on elemental analysis, mass, IR, solid reflectance, magnetic moment, molar conductance, and thermal analyses (TG, DTG and DTA). The molar conductance reveals that all the metal chelates are non-electrolytes. IR spectra shows that L ligand behaves as neutral tridentate ligand and bind to the metal ions via the two azomethine N and pyridine N. From the magnetic and solid reflectance spectra, it is found that the geometrical structures of these complexes are octahedral (Cr(III), Fe(III), Co(II), Ni(II), Cu(II), and Th(IV)) and tetrahedral (Mn(II), Cd(II), Zn(II), and UO2(II)). The thermal behaviour of these chelates shows that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the anions and ligand molecules in the subsequent steps. The activation thermodynamic parameters, such as, E*, ΔH*, ΔS* and ΔG* are calculated from the DTG curves using Coats-Redfern method. The synthesized ligand, in comparison to their metal complexes also was screened for its antibacterial activity against bacterial species, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus pyogones and Fungi (Candida). The activity data shows that the metal complexes to be more potent/antibacterial than the parent Schiff base ligand against one or more bacterial species.     

Uniformity study of wafer-scale InP-to-silicon hybrid integration

β-SiC nanowires were synthesized by a simple carbothermal reduction of carbonaceous silica xerogel. The morphology and structure of the nanowires were investigated by X-ray diffraction, scanning electron microscope and transmission electron microscopy. The results showed that the nanowires were hexagonal prism-shaped hierarchical nanostructures. The typical stacking faults and twin defects of SiC nanowires were also observed. Band-gap characterization and photoluminescence properties of SiC nanowires were investigated by UV-vis absorption spectroscopy and fluorescence photometry, respectively. The results showed the SiC nanowire was an indirect transition semiconductor and the band gap energy for the SiC nanowires was 2.85 eV. The photoluminescence peak value at 470 nm (2.64 eV) originating from the SiC nanowires was a little higher than the value of band-gap energy.     

Spin-orbit symmetries of conduction electrons in silicon

We derive a spin-dependent Hamiltonian that captures the symmetry of the zone edge states in silicon. We present analytical expressions of the spin-dependent states and of spin relaxation due to electron-phonon interactions in the multivalley conduction band. We find excellent agreement with experimental results. Similar to the usage of the Kane Hamiltonian in direct band-gap semiconductors, the new Hamiltonian can be used to study spin properties of electrons in silicon.     

Synthesis, thermal characterization, and antimicrobial activity of lanthanum, cerium, and thorium complexes of amino acid Schiff base ligand

Metal complexes of La(III), Ce(IV), and Th(IV), with the amino Schiff base ligand, [N-(2-hydroxybenzyl)-l-methionine acid](H₃L), were prepared in the presence of triethylamine as a deprotonating agent. All synthesized compounds were identified and confirmed by mass spectra, elemental analyses, molar conductivities, and spectral analyses (UV–Visible, IR, ¹H NMR, and ¹³CNMR). Conductance measurements suggest the non-electrolytic nature and the complexes were isolated in 1:1 ratios. The thermal decomposition of the complexes was discussed in relation to structure. The data from thermogravimetric analysis clearly indicated that the decomposition of the complexes proceeds in four or five steps and the organic part of the complexes decomposed in one or two intermediates. The decomposition of all complexes ended with metal oxide and carbon residue. The Schiff bases and their complexes were screened for their antibacterial (Escherichia coli, Staphylococcus aureus) and antifungal (Aspergillus flavus and Candida Albicans) activities.     

Synthesis, spectroscopic, thermal characterization, and antimicrobial activity of miconazole drug and its metal complexes

Metal complexes having the general composition [MCl₂(H₂O)₂(L)₂]·yH₂O (where y?=?1?C3, M?=?Mn(II), Cu(II), Co(II), Ni(II), and Zn(II) and L?=?miconazole drug?=?MCNZ) and [MCl₂(H₂O)₂(L)₂]Cl·3H₂O (where M?=?Cr(III) and Fe(III)) have been synthesized. All the synthesized complexes were identified and confirmed by elemental analyses, IR, diffused reflectance, and thermal analyses (TG and DTA) techniques as well as molar conductivity and magnetic moment measurements. The molar conductance data reveals that bivalent metal complexes are non-electrolytes while Cr(III) and Fe(III) complexes are electrolytes and of 1:1 type. IR spectral studies reveal that MCNZ is coordinated to the metal ions in a neutral unidentate manner with N donor site of the imidazole-N. On the basis of magnetic and solid reflectance spectral studies, an octahedral geometry has been assigned for the complexes. Detailed studies of the thermal properties of the complexes were investigated by thermogravimetry (TG) and differential thermal analyses (DTA) techniques and the activation thermodynamic parameters are calculated using Coats?CRedfern method. The free MCNZ drug and its complexes were also evaluated against bacterial species (P. aeruginosa, S. aureus, B. subtilis, E. Coli) and fungi (A. fumigatus, P. italicum, and C. albicans) in vitro. The activity data show that the metal complexes have higher biological activity than the parent MCNZ drug.     

Fine-tuning the luminescence and HOMO-LUMO energy levels in tetranuclear gold(I) fluorinated amidinate complexes

Tetranuclear gold(I) fluorinated amidinate complexes have been synthesized and their photophysical properties and structures described. DFT calculations were carried out to illustrate how a minor change in the ligand resulted in a loss of emission in the perfluorophenyl amidinate complex compared with nonfluorinated phenyl amidinate complexes reported previously. The fluorinated complexes reported here [Au(ArN)(2)C(H)](4) (1, Ar = 4-FC(6)H(4); 2, 3,5-F(2)C(6)H(3); 3, 2,4,6-F(3)C(6)H(2); 4, 2,3,5,6-F(4)C(6)H) emit in the blue-green region at 470, 1, 478, 2, 508, 3, and 450 nm, 4, by excitation at ca. 375 nm at room temperature with nanosecond lifetimes. The emissions observed at 77 K in the solid state show structured emission for complexes 1 and 2, with a vibrational spacing of ca. 1200 and 1500 cm(-1), corresponding to the vibrational modes of the amidinate ligand. The pentafluorophenyl derivative 5, Ar = C(6)F(5,) shows no photoluminescence in the solid state nor in the solution. This result is different from results in which the pentafluorophenyl group is attached to a phenylpyridine ligand in an Ir(III) complex and other organics. This quenching appears to be related to a nonradiative de-excitation process caused by the ππ*-πσ* crossover in the excited state of the pentafluorophenyl amidinate ligand. With increasing numbers of fluorine atoms, there is a progressive decrease in the contribution of the amidinate ligands to the corresponding HOMO orbital. There also is a slight decrease in the ligand contribution to the LUMO with increased numbers of fluorine atoms and an exchange of the character of the orbitals of the gold centers.     

Glycosides from Bougainvillea glabra

Three glycosides were isolated from Bougainvillea glabra and their structures were determined by extensive use of 1D and 2D NMR spectroscopy ((1)H and (13)C). First compound was identical to momordin IIc (quinoside D) [beta-D-glucopyranosyl 3-O-[beta-D-xylopyranosyl-(1 --> 3)-O-(beta-D-glucopyranosyluronic acid)] oleanolate], second compound was quercetin 3-O-alpha-L-(rhamnopyranosyl)(1 --> 6)-[alpha-L-rhamnopy-ranosyl(1 --> 2)]-beta-D-galactopyranoside and third compound was its derivative quercetin 3-O-alpha-L-(4-caffeoylrhamnopyranosyl)(1 --> 6)-[alpha-L-rhamnopyranosyl (1 --> 2)]-beta-D-galactopyranoside, a new natural product.     

Evaluation of Substituted Pyrazole-Based Kinase Inhibitors in One Decade (2011–2020): Current Status and Future Prospects

Pyrazole has been recognized as a pharmacologically important privileged scaffold whose derivatives produce almost all types of pharmacological activities and have attracted much attention in the last decades. Of the various pyrazole derivatives reported as potential therapeutic agents, this article focuses on pyrazole-based kinase inhibitors. Pyrazole-possessing kinase inhibitors play a crucial role in various disease areas, especially in many cancer types such as lymphoma, breast cancer, melanoma, cervical cancer, and others in addition to inflammation and neurodegenerative disorders. In this article, we reviewed the structural and biological characteristics of the pyrazole derivatives recently reported as kinase inhibitors and classified them according to their target kinases in a chronological order. We reviewed the reports including pyrazole derivatives as kinase inhibitors published during the past decade (2011–2020).     

Gas-phase kinetics of elimination reactions of pentane-2,4-dione derivatives. Part ii [1]. Thermolysis of derivatives and analogues of 3-phenylhydrazonopentane-2,4-dione

Six analogues and derivatives (1–6) of 3-phenylhydrazonopentane-2,4-dione (7) were subjected to gas-phase thermolysis. The Arrhenius log A (s⁻¹) and Ea (kJ mol⁻¹) of the analogues (1–5) are, respectively: 10.42 and 140.8 for 1-cyano-1-phenyl-hydrazonopropanone (1) , 11.19 and 135.4 for 1-cyano-1-( -nitrophenylhydrazono)-propanone (2) , 10.68 and 144.9 for 1-cyano-1-( -methoxyphenylhydrazono)propanone (3) , 11.76 and 137.8 for 1-cyano-3-phenyl-1-phenylhydrazonopropanone (4) , and 11.29 and 145.9 for 1-cyano-1-phenylhydrazonobutanone (5) . The corresponding values for ethyl 3-oxo-2-phenylhydrazonobutanoate (6) are 11.90 s⁻¹ and 143.3 kJ mol⁻¹. The rates of reaction at 600 K are compared with those of the title diketone (7) and of pentane-2,4-dione (8) and rationalized in terms of a plausible elimination pathway involving a semiconcerted six-membered transition state. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 457–462, 1998